Add 8bit and binary decoding support DusanKasan#37

parsemail.go

@@ -484,7 +484,7 @@ func decodeContent(content io.Reader, encoding string) (io.Reader, error) {
         }
 
         return bytes.NewReader(b), nil
-    case "7bit":
+    case "7bitt", "8bit", "binary":
         dd, err := ioutil.ReadAll(content)
         if err != nil {
             return nil, err